The present invention relates to water soluble compounds and their salts, to compositions containing such compounds and their use in ink jet printing (xe2x80x9cIJPxe2x80x9d), to ink jet printer cartridges and to ink jet printing processes.
IJP is a non-impact printing technique in which droplets of coloured liquids are ejected through a fine nozzle onto a substrate without bringing the nozzle into contact with the substrate.
IJP is a relatively inexpensive way of recording multicolour images, for example pictures obtained from digital sources such as electronic cameras, scanners and the Internet. The use of ink jet printers to print colour images in the home or office environment is now becoming commonplace. However IJP has a big disadvantage compared to conventional silver halide photography in that the resultant images fade in ordinary daylight. Thus, there is a need to improve the light-fastness properties of prints to prevent images fading or vanishing, or becoming discoloured over time. In addition, there are many demanding performance requirements for dyes and inks used in IJP. For example sharp, non-feathered images having good water-fastness and optical density are required. The inks are required to dry quickly when applied to a substrate to prevent smudging, but they should not form a crust over the tip of an ink jetnozzle which stops the printer from working effectively. The inks should also be stable to storage over time without decomposing by forming a precipitate which could block the fine nozzle.
The choice of a colorant in ink jet systems is critical to image quality. The colorants should also have a high degree of light-fastness after printing onto a substrate. For aqueous dye-based inks, the dyes need to be sufficiently soluble in water to prepare a solution that is capable of producing adequate density on the substrate and be stable for extended periods of storage without precipitation. It is difficult to find dyes which meet all of these requirements, particularly yellow dyes.
U.S. Pat. Nos. 4,393,132, 4,183,755 and 4,148,643 disclose the formation of metal chelating compounds in the course of a reaction during photographic development followed by diffusion into a photographic image receiving layer in which the metallised dye is formed and immobilised. These patents do not specify the use of premetallised dyes and only refer to the formation of metal complexes on diffusion of the dye into the image receiving layer.
European patent 260,561 describes the use of related compounds for dyeing leather.
German OLS 2404314 describes certain formulations of Cr and Co coordinated dyes which would not be suitable as ink jet inks.
Water immiscible yellow dyes are described in U.S. Pat. Nos. 4,407,931 and 4,418,131 and are useful in photographic applications.
According to the present invention there is provided a water soluble compound of Formula (1) or a salt thereof: 
wherein:
Y is an electron withdrawing group;
Y1 is H,alkyl or aryl, OR or NR2 in which each R independently is H, optionally substituted alkyl or optionally substituted aryl;
or Y and Y1 together form a 5- or 6- membered ring;
X1 is a group or atom which co-ordinates with M;
M is hexa co-ordinate metal;
G is a group of Formula (2), (3) or (4); and
L1, L2 and L3, each independently represent ligands required to complete hexa-coordinate geometry around metal M; 
xe2x80x83wherein:
S is a water solubilizing group;
Ar is a benzene or naphthalene group in which X is located ortho to the azo group;
X is a group or atom which co-ordinates with M;
Z provides atoms or groups which complete an optionally substituted 5- or 6-membered aromatic heterocyclic ring;
Ring A is an optionally substituted aromatic ring;
Ring B is an optionally substituted 5- or 6-membered aromatic heterocyclic ring;
n is 0, 1, 2 or 3;
and the * signify the points of attachment of the groups of Formulae (2), (3) and (4) to the N and M atoms in the compound of Formula (1).
The compounds of Formula (1) preferably comprise at least one water solubilising group which is preferably a carboxy, amido, sulpho, sulphonamide or phosphato group which is preferably present in Y or Y1, or is a substituent on Ring B or on Ring A preferably in a position para with respect to the azo group.
Y is preferably selected from CN, CO2H, CO2R, CONR2, COR and xe2x80x94SO2NR2 in which each R is independently defined as above.
Where Y1 is alkyl it is preferably C1-8-alkyl, more preferably C1-4-alkyl.
Where Y1 is aryl it is preferably phenyl.
Where R is optionally substituted alkyl it is preferably C1-8-alkyl, more preferably C1-4-alkyl.
Where R is optionally substituted aryl it is preferably phenyl or naphthyl, more preferably phenyl.
Where R is optionally substituted alkyl or aryl optional substitutents are preferably selected from water solubilising groups, particularly SO3H, SO2NR2, CO2H or PO3H2.
Where Y and Y1 are joined together to form a 5- or 6-membered ring it is preferably pyrazolone or triazole, more preferably pyrazolone or 1, 3, 4-triazole.
X and X1 each independently is preferably O, CO2R or NR in which R is defined above. Where X or X1 is CO2R co-ordination to the metal occurs through an O atom and the C atom to which it is attached is included to form a 6 -membered ring.
M is preferably Zn2+, Cu2+, Co2+, Co3+, Pt2+, Pd2+, Cr3+or Ni2+.
Optional substitutents for Rings A and B are preferably selected from C1-4-alkyl, aryl, SO3H, SO2NR2, CO2H or PO3H2 in which R is as defined above.
In a first preferred embodiment of the present invention in the compound of Formula (1) G is a group of Formula (2), this is shown below as the compound of Formula (5). 
in which Y, Y1, X, X1, M, Ar, L1, L2, L3, S and n are as defined above.
In a second preferred embodiment of the present invention in the compound of Formula (1) G is a group of Formula (3), this is shown below in the compound of Formula (6). 
in which Y, Y1, X1, M, L1, L2, L3, Z, S, Ring B and n are as defined above.
In a third preferred embodiment of the present invention in the compound of Formula (1) G is a group of Formula (4), this is shown below as the compound of Formula (7); 
in which Y, Y1, X1, M, L1, L2, L3, Z and Rings A and B are as defined above.
In a further preferred embodiment of the present invention in the compound of Formula (1) is G is a group of Formula (4):
Z preferably comprises a chain of two or three carbon atoms or one or two carbon atoms and one nitrogen atom, more preferably Z is of formula xe2x80x94CR2xe2x95x90CR2xe2x80x94CR2xe2x95x90wherein each R2 is independently H or a substituent, of which one may be a hydrophilic group for example a carboxy, amido, sulpho, sulphonamide or phosphate group in order to increase the water solubility of the compound; it is preferred that any non hydrophilic substituent is H. It is especially preferred that X forms part of a quinoline group;
X1 is preferably O or NR3 wherein R3 is H or optionally substituted alkyl.
Y is preferably CN, CONR4R5, SO2NR4R5, COR4 or CO2R4 wherein R4 and R5 are each independently H or C1-4-alkyl groups which may be substituted by water-solubilising groups preferably carboxy, amido, sulpho, sulphonamide or phosphato groups;
or R4 and R5 together with the nitrogen atom to which they are attached form a 5- or 6-membered ring;
M is preferably Zn2+, Cu2+, Co2+, Co3+, Pt2+, Pd2+, Cr3+ or Ni2+, more preferably Ni2+; and
L1, L2 and L3 represent three monodentate ligands, one bidentate ligand and one monodentate ligand or one tridentate ligand.
Monodentate ligands include cosolvents for the compound, for example lower alcohols (for example C1-6-alkylOH, preferably C1-4-alkylOH), tetrahydrofuran or ammonia.
The ligands L1, L2 and L3 may be 3 separate independently selected monodentate ligands, or a monodentate ligand and a bidentate ligand or preferably a tridentate ligand; preferred tridentate ligands represented by L1, L2 and L3 collectively are ligands of either Formula (8), Formula (9) or Formula (10) where Y, Y1, X, X1, Z, Ar, S, n and Rings A and B are as defined above and which incorporate water-solubilizing groups as mentioned above. 
In a particularly preferred embodiment the compounds of Formulae (5) and (6) are symmetrical 2:1 complexes of Formulae (11) and (12) wherein each Ar, X, X1, Y, Y1, Z, S, n, Ring B and M are as hereinbefore defined. 
M in Formula (5) is preferably Zn2+, Cu2+, or Ni2+, more preferably Ni2+ and M in Formula (6) is preferably Zn2+, Cu2+, Co2+, Co3+, Cr3+ or Ni2+, more preferably Ni2+.
A preferred tridentate ligand represented by L1, L2 and L3 collectively is a ligand of Formula (10) in which Y, Y1, X1, Z, and Rings A and B are as defined above and which possesses water-solubilising groups as specified for R above: 
A particularly preferred embodiment the compound of Formula (1) is of Formula (13): 
in which each X1, Y, Y1, Z, M and Rings A and B are each independently as defined above.
In compounds of Formula (13) the preferences for X1, Y, Y1, Z, M and Rings A and B are as hereinbefore defined for the compounds of Formula (1).
The above compounds are preferably yellow dyes.
According to a further feature of the present invention there is provided a liquid ink composition suitable for ink jet printing which comprises an aqueous liquid medium and, dissolved therein, one or more compound(s) of Formulae (1), (5), (6), (7), (11), (12) and (13).
A preferred composition comprises:
(a) from 0.01 to 30 parts of a compound of the Formula (1), more preferably of Formula (3); and
(b) from 70 to 99.99 parts of the liquid medium;
wherein all parts are by weight and the number of parts of (a)+(b)=100.
Preferred liquid media include water or a mixture of water and one or more organic solvents.
When the liquid medium comprises a mixture of water and organic solvent, the weight ratio of water to organic solvent is preferably from 99:1 to 1:99, more preferably from 99:1 to 50:50 and especially from 95:5 to 80:20.
It is preferred that any organic solvent present in the mixture of water and organic solvent is water-miscible. Preferred water-miscible organic solvents include C1-6-alkanols, preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, cyclopentanol and cyclohexanol; linear amides, preferably dimethylformamide or dimethylacetamide; ketones and ketone-alcohols, preferably acetone, methyl ether ketone, cyclohexanone and diacetone alcohol; water-miscible ethers, preferably tetrahydrofuran and dioxane; diols, preferably diols having from 2 to 12 carbon atoms, for example pentane-1,5-diol, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol and thiodiglycol and oligo- and poly-alkyleneglycols, preferably diethylene glycol, triethylene glycol, polyethylene glycol and polypropylene glycol; triols, preferably glycerol and 1,2,6-hexanetriol; mono-C1-4-alkyl ethers of diols, preferably mono-C1-4-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)-ethanol, 2-[2-(2-methoxyethoxy)ethoxy]ethanol, 2-[2-(2-ethoxyethoxy)-ethoxy]-ethanol and ethyleneglycol monoallylether; cyclic amides, preferably 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, caprolactam and 1,3-dimethylimidazolidone; cyclic esters, preferably caprolactone; sulphoxides, preferably dimethyl sulphoxide and sulpholane. Preferably the liquid medium comprises water and 2 or more, especially from 2 to 8, water-soluble organic solvents.
Especially preferred water-miscible organic solvents are cyclic amides, especially 2-pyrrolidone, N-methyl-pyrrolidone and N-ethyl-pyrrolidone; diols, especially 1,5-pentane diol, ethyleneglycol, thiodiglycol, diethyleneglycol and triethyleneglycol; and mono-C1-4-alkyl and C1-4-alkyl ethers of diols, more preferably mono-C1-4-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxy-2-ethoxy-2-ethoxyethanol.
Examples of further suitable ink media comprising a mixture of water and one or more organic solvents are described in U.S. Pat. Nos. 4,963,189, 4,703,113, 4,626,284 and EP 4,251,50A.
The solvent preferably has a boiling point of from 30xc2x0 to 200xc2x0 C., more preferably of from 40xc2x0 to 150xc2x0 C., especially from 50 to 125xc2x0 C.
The liquid medium may also contain additional components conventionally used in ink jet printing inks, for example viscosity and surface tension modifiers, corrosion inhibitors, biocides (e.g. Proxel from Avecia Ltd), humectants, kogation reducing additives and surfactants which may be ionic or non-ionic.
Surfactants may be included in the liquid medium to adjust the surface tension of the compositions to an appropriate level. The surfactants are preferably anionic, cationic, amphoteric or nonionic.
Preferably the composition has been filtered through a filter having a mean pore size below 10 xcexcm, more preferably below 5 xcexcm, especially below 2 xcexcm, more especially below 1 xcexcm. In this way particulate matter is removed which could otherwise block the fine nozzles used in ink jet printers.
Preferably the composition has a viscosity of below 20 cp, more preferably below 10 cp, especially below 5 cp, at 20xc2x0 C.
Preferably the compounds described herein have been purified by reverse osmosis, ultra-filtration, ion exchange or a combination thereof, either before or after they are incorporated in a liquid ink composition according to the present invention.
Preferably the liquid composition is yellow.
A further feature of the present invention provides a process for printing an image on a substrate comprising applying thereto by means of an ink jet printer a liquid ink composition which comprises an aqueous medium and dissolved therein one or more compounds of formulae (1), (5), (6), (7), (11), (12), and (13).
The ink jet printer preferably applies the composition to the substrate in the form of droplets which are ejected through a small orifice onto the substrate. Preferred ink jet printers are piezoelectric ink jet printers and thermal ink jet printers. In thermal ink jet printers, programmed pulses of heat are applied to the composition in a reservoir by means of a resistor adjacent to the orifice, thereby causing the composition to be ejected in the form of small droplets directed towards the substrate during relative movement between the substrate and the orifice. In piezoelectric ink jet printers the oscillation of a small crystal causes ejection of the composition from the orifice.
A further feature of the invention provides an ink jet printer cartridge, optionally refillable, containing a liquid ink composition which comprises an aqueous medium and dissolved therein one or more compounds of formulae (1), (5), (6), (7), (11), (12), and (13).
The substrate is preferably paper, plastic, a textile, metal or glass, more preferably paper, an overhead projector slide or a textile material, especially paper.
Preferred papers are plain or treated papers which may have an acid, alkaline or neutral character.
A further aspect of the present invention provides separately a paper, an overhead projector slide and a textile material printed with a liquid ink composition according to the present invention or by means of a process as defined above.
When the substrate is a textile material the liquid ink composition of the present invention is preferably applied thereto by:
i) applying the ink to the textile material using an ink jet printer; and
ii) heating the printed textile material at a temperature of from 50xc2x0 C. to 250xc2x0 C.
Preferred textile materials are natural, synthetic and semi-synthetic materials. Examples of preferred natural textile materials include wool, silk, hair and cellulosic materials, particularly coffon, jute, hemp, flax and linen. Examples of preferred synthetic and semi-synthetic materials include polyamides, polyesters, polyacrylonitriles and polyurethanes.
Preferably the textile material has been treated with an aqueous pre-treatment composition comprising a thickening agent and optionally a water-soluble base and a hydrotropic agent and dried prior to step i) above.
The pre-treatment composition preferably comprises a solution of the base and the hydrotropic agent in water containing the thickening agent. Particularly preferred pre-treatment compositions are described more fully in European Patent Application No.534660.
The invention also provides a process of ink jet printing in which droplets of a liquid ink composition according to the invention are deposited on a suitable substrate.